Some 15 million tonnes of food is wasted in the UK every year, according to estimates by the Waste and Resources Action Programme (Wrap).

The majority occurs at farm level, but campaigners say that supermarkets have a role to play well beyond their premises.

Domnika Jarosz, of campaign group Feeding the 5000, said supermarkets "control a large part of the supply chain".

"Their strict cosmetic standards - which reject straight bananas and cracked cauliflowers, for example - mean there is a significant amount of waste before products even reach the shelf," she told ITV News.

The findings also show that a significant proportion of wastage occurs in households. One in three bagged salads is thrown away at home, and one in four apples.

The average family spends £700 per year on food that is never eaten, the research shows.